Had my '56 Grande Punto for nearly 3 years now, fearing a new gearbox & clutch replacement soon £££

Tell me what you think of these symptoms;

Last week slight whine noise from 1st, 2nd & little bit of 3rd under acceleration, otherwise it was fine.
Drove all the way south (400km) non-stop, in 5th+6th all the way, as soon as i reached the first set of lights down there and pulled away the whine was massively loud, again 1st, 2nd & 3rd.

Here's me thinking its just getting old, new box oil and it'll be fine..... I was so wrong.

Started driving back up after the weekend, it started out better, the whine went back to being quiet and I was pleased
Doing 70mph (scouts honor) on the M1 the engine suddenly revved because it had lost the gear, put the clutch down to try and re-engage 6th but the clutch pedal stayed down.
Tried 5th instead but the clutch stayed down. Gear stick was engaging each gear but the clutch was not having it. So I coasted over to the hard shoulder, engine off, back on and I did a test.
Lifted the clutch up with the top of my foot, and then it sprung itself up a few times, 1st, 2nd and reverse seemed to bite, so I started of again.
1st, 2nd and 3rd worked as usual, albeit with the whine, 4th worked again with no whine (small victories). 5th however didn't work, the clutch stayed down, so again I lifted the clutch up manually in gear and got 5th, tried again for 6th, same thing, had to lift the clutch manually to bite 6th.
Then in 6th, grinding noise from the gearbox, like just grinding gears except fainter, down to 5th for a bit, intermittently the faint grind was there, so I managed to get to the services and was rescued by Green Flag.

So, clutch doesn't spring back up in 5th or 6th.
Gearbox whines in 1st, 2nd and 3rd.
Grinds faintly in 5th and 6th.

What do you reckon? Clutch, gearbox or both? Replacements or repairs?

1.9 MJet 70k miles
Orig gearbox & clutch as far as I know.
Spirited driving but never over revved on down shift (which I read a lot about with others on gearbox problems)

Possibly both clutch and box here but to be honest, you'd be changing the clutch anyway when doing the box. Assuming it has one, have a look at the slave cylinder on top of the box to see if there's anything amiss with it.